The invention relates to an apparatus that is designed and intended for de-icing the surface of a casing tube of a tendon, which tube is exposed to weather influences, and/or to guard against, if not completely prevent, ice forming on said tube, the tendon being anchored to a structure by means of an anchoring device.
The formation of ice on the outer surface of the casing tubes of tendons that are built on structures, for example the formation of ice on the outer surface of the casing tubes of stay cables of bridges, poses considerable problems for the companies or authorities responsible for operating the structures. It may therefore be the case, for example, that stay cable bridges have to be closed to traffic in order to prevent vehicles travelling over the bridge from being damaged or, even worse, the passengers of said vehicles from being injured, by falling lumps of ice that have broken away from the stay cables.
Various procedures have been used in the past to remove the ice from the stay cables:
For example, workers were transported along the stay cables in lifting cages of cranes, so that said workers could chip the ice from the stay cables. Attempts were also made to cause the stay cables to oscillate, by means of helicopters flying close to the bridge, so that the ice broke off the stay cables. These two approaches were highly time-consuming, laborious and ineffective.
A further procedure consisted in allowing chain rings placed around the stay cables to slide along the stay cable, one after the other, from the upper anchoring device to the lower anchoring device. This solution is disadvantageous, however, in that the chain rings on the lower anchoring device have to be removed from the stay cable and transported back to the upper anchoring device. Furthermore, damage to the rain-repelling ribs arranged on the outside of the casing tube is unavoidable.
Furthermore, it is known to generate pulses by means of electromagnetic coils, which pulses spread along the casing tube and are intended to make the ice break off the casing tube mechanically. However, this approach is disadvantageous because of its high power consumption.
Finally, thermal approaches have also been explored, in which the layer of ice is intended to be melted at least in part, either by blowing warm air through the casing tube or by ohmic heating of a steel foil surrounding the casing tube, in order to make it easier for the ice to break off the casing tube. The high power consumption involved is also disadvantageous in this approach.
The object of the present invention is to provide an alternative that is cost-effective to produce and operate.